If you’re under 40, the term polar vortex may be new to you, but it’s happening now in the mid-west. Windchills of nearly -60C (-70F) are threatening to turn states in the north and northwest US into an icy deep freeze, thanks to super-chilled air from the Arctic into North and South Dakota, the Great Lakes states and New England, sending temperatures plunging. Continue reading for more natural phenomena you might not have known about.